Přírodní výběr ad usum filosofů

This article provides a survey of conceptions which, in contemporary, largely naturalistically-orientated, evolutionary biology, broaden or break free of the so-called modern synthesis (here roughly synonymous with “selectionism”) - that is the stand­point according to which natural selection is by far the most important cause of the evolutionary process. Since the 1960’s a competitor has arisen to selectionism in the shape of the so-called “neutral theory” of evolution, according to which many genetic mutations are adaptively neutral and appear in the genome with frequencies that should be put down to chance (genetic drift) rather than to selection. The main stream of evolutionary biology today is coming to a certain compromise between these two approaches: it tends to allow neutralism at the level of molecular evolution, but to recognise the action of selection on mutations evinced at the level of the phenotype. The possibility of the sequencing of whole genomes has opened up the area of comparative genomics which, on one hand, has led to the reinforcement of neutralism especially in multi-celled organisms (Michael Lynch) but, on the other hand, has led to the recognition of the decisive role of the horizontal transfer of genes in microbes in the so-called pre-Darwinian phase of evolution (Carl Woese). This phase is interpreted as mainly non-selective, if not “Lamarckian”, and in each case it certainly entails the demise of the idea of a common ancestor and of evolution by small steps. A further corrective has been the emphasis of the fact that selection draws on material prepared by the duplication of genes or of whole genomes (Susumu Ohno). Beyond any possibility of analytical elaboration in population genetics there still remains the conception of so-called regulatory evolution (S. Carroll, E. Davidson) which, at a certain point, even results in the denial of the possibility of evolution by small steps. A particularly new standpoint, often put forward in direct contradiction to the current mainstream of evolutionary biology, presents a conception which is bound to the formal theory of dynamic systems and methodologically to the mathematical modelling of regulatory networks. It most frequently goes by the name of self-organisation or emergentism. Without denying the important role of selection, it puts constraints on it by pointing to the inner-organisational principles of living beings which, however, ultimately arise from basic physical laws. The principles of self-organisation indicate one path by which greater complexity of organisms and their components may be achieved in evolution. - Selectionism is confronted not only by the pressure of these unorthodox evolutionary approaches, but also by several unanswered internal questions emphasised by professional evolutionists themselves (among them Lewontin and Gould). A heavy penalty has been paid for the constitution of the theoretical basis of evolutionary biology – population genetics, namely the splitting of the individual organism into a genotype and a phenotype and the subsequent atomisation of both into isolated genes and their alleles on the one hand, and the isolated characteristics of the phenotype on the other. From that point of departure - according to the system-oriented authors - the evolutionary emergence of organic mega-complexity as such is rendered an insoluble problem (let alone the emergence of organic proto-subjectivity which, however, is beyond the scope of this survey). Not even long-term evolutionary trends are satisfactorily explained, according to the opinion of many authors. Selectionism is criticised for its facile appeal to “evolutionary just-so stories” which elude all possibility of verification. Overall, (naturalistic) evolutionary biology today recognises three principle evolutionary “mechanisms”: selection, genetic drift and self-organisation. This science is, however, in a state of rapid development and unexpected “emergences” in its own future progress cannot be ruled out - on the contrary. It would be very unwise for philosophers, who thematically draw on an evolutionary-biological base, to put all their faith in natural selection as the single decisive force in organic evolution - that would be to ignore the range and importance of the changes which evolutionary biology has undergone in the last decades.